This invention relates to fission product disposal in permanent icefields.
One of the major impediments to the social acceptance of nuclear power is the still unresolved question of the disposal of the radioactive high level waste from nuclear reactors. Presently the spent fuel rods are mostly being stored on site and the solution to the problem being postponed. Meanwhile, spent fuel from most of the world""s reactors accumulates and the problem becomes ever more serious. The longer a decision on the method of disposal to be used is postponed, the greater becomes the probability of a serious nuclear related accident or intentionally motivated major incident.
The solution to the disposal problem has to ensure the safe isolation of the radioactive waste from the biosphere while it remains hazardous. Technically this should not be a major problem, but it has to be done in an environmentally and socially acceptable manner, as well as in a manner to insure inaccessibility for security reasons.
Simply put, a debt that is owed to future generations is to minimize the hazard from the radioactive legacy that we have already left them. It takes hundreds of thousands of years for the ingestion hazard index from unreprocessed spent fuel from light water reactors to diminish until it is no more than that from the naturally occurring uranium that the fuel originated from. (See for ex. Benedict, M., Pigford, T. H., Levi H. W., Nuclear Chemical Engineering, McGraw Hill Book Company, New York, 1981, p.573 and p.623). If, on the other hand, the fuel is reprocessed and the actinides removed and disposed of, that time can be shortened to a time span of the order of a thousand years. Hence, for a cleaner future environment one should preferably also reclaim andxe2x80x9cburnxe2x80x9d the plutonium that presently exists in spent nuclear fuel. For example, according to Albright, F. B., Walker, W., World Inventory of Plutonium and Highly Enriched Uranium 1992, Oxford University Press, Oxford, 1993, the sum of already accumulated spent nuclear fuel and that which is projected to the year 2000 is about 220,000 tonnes. At a burnup, roughly estimated, of 30,000 Mwd/tonne (of fuel) this corresponds to thermal energy production of 6,600,000,000 Mwd. Since each Megawatt-day of energy production is accompanied by the formation of just about 1.04 g. of fission products the quantity of fission products accumulated worldwide up to the end of the millenium is close to 7,000 tonnes.
The corresponding Plutonium content of the spent fuel is estimated at 1390 tonnes, if all this is fissioned it corresponds to an additional 1,338,000,000 Mwd or 20% of the energy already realized from the spent fuel. With continuous reprocessing and recycling that converts more Uranium-238 into plutonium that figure roughly doubles adding yet another 20%. Apart from providing energy the recycled Plutonium would be disposed of as a very long lived radiation hazard and potential nuclear weapons material.
Accordingly, it can be seen that there is a real and a continuing need for safe effective disposal of fissile isotopes and fission products in a manner that creates no environmental hazard for present or future generations. This invention has, as its primary objective, helping to fulfill this need.